It is known that a number of natural products have insect repellent properties. Citronella oil, which is obtained from certain grasses is one example of such a natural product, and oil from the Neem tree is another. We have previously investigated certain insect repellent natural products and have found that the insect repellent properties are in a fraction rich in p-menthane-3,8-diol (PMD). This is described in our GB-A-2282534. In GB-A-1315625, there is described the use of certain p-menthane diols, but not PMD, to provide a physiological cooling effect.